Field of the Invention
The present invention relates to a bisimidazolidene compound, an organic light emitting element containing the same and a display device.
Description of the Related Art
An organic light emitting element is an element containing an anode and a cathode, and an organic compound layer arranged between both electrodes. In the organic light emitting element, excitons are generated by recombination of holes and electrons injected from the above each electrode in a light emitting layer, which is an organic compound layer, and light is released when the excitons return to the ground state. With the recent significant advances in organic light emitting elements, it is possible to make a slim lightweight light emitting device which has low driving voltage, diverse light emission wavelengths and high responsivity.
In an organic light emitting element, improvements in electron injection properties are preferred to lower voltage to drive the element. As a technique to improve electron injection properties, a technique in which metals are used in electron injection layers of an organic light emitting element is described in Japanese Patent Application Laid-Open No. 2003-68468 and Japanese Patent Application Laid-Open No. 2002-100482.
In addition, the synthesis method of a compound like 1-A is described in Journal of American Chemical Society, 1964, 86(12), pp 2518-2519. The use of this compound for a photo conductor is described in Japanese Patent Application Laid-Open No. S63-280254; however, there is no description about using the compound for an organic light emitting element.

In Japanese Patent Application Laid-Open No. 2003-68468 and Japanese Patent Application Laid-Open No. 2002-100482, an organic light emitting element in which metals are contained in electron injection layers is described. This organic light emitting element contains metals in the electron injection layers. Thus, a stable organic light emitting element cannot be obtained. This is because these metals have high reactivity to moisture.
Because these metals react with moisture, stability as an organic light emitting element decreases.